Perineurial Cells and Nerve Axons inGastrointestinal Schwannomas: a Similaritywith Neurofibromas.An Immunohistochemical Study of Eight Cases

Overview

Gastrointestinal schwannoma (GIS) is a distinctive and extremely rare lesion showing some differencesfrom conventional soft tissue schwannoma and some similarities with common soft tissueneurofibroma. Soft tissue neurofibromas and schwannomas differ by contents of specific types ofnerve sheath cells, such as Schwann cells, perineurial cells and CD34+ cells. To compare GIS withthese soft tissue lesions, eight cases of typical GIS were studied immunohistochemically to evaluatetheir nerve sheath cell types. Epithelial membrane antigen (EMA) and claudin-1 as perineurialcell markers, and neurofilament protein as a marker for intratumoral axons were used. In addition,the tumors were stained for cytokeratin, CD117 (C-KIT), alpha-muscle specific actin, S100protein and CD34. EMA- and claudin-positive cells were seen in 2 (25%) and one lesion, respectively,thus resembling cellular composition of neurofibroma. Intratumoral neurofilament proteinpositive axons otherwise typical of neurofibroma were found inside 4 tumors (50%). CD34 positivitywas found in 6 tumors (75%) and often revealed a diffuse pattern as seen in neurofibroma andnot a zonal pattern as described in schwannomas. These results show that GIS has some featuresthat are more typical for neurofibroma than for conventional schwannoma. In surgical pathologypractice, a finding of intratumoral axons and positivity for claudin-1 and especially for EMAshould not preclude diagnosis of GIS.

Key words:
gastrointestinal schwannoma – neurofibroma – perineurial cell – nerve axon – immunohistochemistry